U.S. patent number 4,810,838 [Application Number 07/070,912] was granted by the patent office on 1989-03-07 for frequency coupling position coordinates determination apparatus.
This patent grant is currently assigned to NEC Corporation. Invention is credited to Kazuo Ichinokawa, Tadashi Otsuka, Yoichi Sato.
United States Patent |
4,810,838 |
Ichinokawa , et al. |
March 7, 1989 |
Frequency coupling position coordinates determination apparatus
Abstract
A frequency coupling position coordinates determination
apparatus includes sheet means on which N (positive integer)
one-turn coils for detecting a magnetic force and M (less than N)
signal lines to which at least one predetermined one-turn coil of
the N one-turn coils is connected are arranged, and detecting means
for detecting the amplitudes of currents respectively flowing
through the M signal lines.
Inventors: |
Ichinokawa; Kazuo (Tokyo,
JP), Sato; Yoichi (Tokyo, JP), Otsuka;
Tadashi (Tokyo, JP) |
Assignee: |
NEC Corporation
(JP)
|
Family
ID: |
15906551 |
Appl.
No.: |
07/070,912 |
Filed: |
July 8, 1987 |
Foreign Application Priority Data
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Jul 18, 1986 [JP] |
|
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61-170525 |
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Current U.S.
Class: |
178/18.07 |
Current CPC
Class: |
G06F
3/046 (20130101) |
Current International
Class: |
G06F
3/033 (20060101); G08C 021/00 () |
Field of
Search: |
;178/19,18 ;364/188 |
References Cited
[Referenced By]
U.S. Patent Documents
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4644102 |
February 1987 |
Blesser et al. |
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Primary Examiner: Schreyer; Stafford D.
Attorney, Agent or Firm: Laff, Whitesel, Conte &
Saret
Claims
What is claimed is:
1. A frequency coupling, position coordinates determination
apparatus comprising:
cursor means for generating a magnetic flux of a predetermined
frequency with respect to a position of said cursor on a sheet
means, coordinates of said position of said cursor means on said
sheet means being the coordinates which are to be determined by
said apparatus;
a number of one-turn coils, arranged parallel to each other at an
equal interval on said sheet means, for detecting the magnetic flux
generated by said cursor means, the interval being set such that P
one-turn coils of said plurality of one-turn coils are covered by
said cursor means;
a number of signal lines which are fewer than the number of said
plurality of one-turn coils and which are connected to said
plurality of one-turn coils in a predetermined correspondence set
such that a combination of said signal lines to which given
adjacent P one-turn coils are connected differs from a combination
of said signal lines to which other given adjacent P one-turn coils
are connected;
detecting means for detecting a current flowing through said
respective signal lines; and
calculating means for calculating the position coordinates of said
cursor means on said sheet means on the basis of an output from
said detecting means.
2. A frequency coupling, position coordinates determination
apparatus comprising:
cursor means for generating a magnetic flux of a predetermined
frequency with respect to a position of said cursor on a sheet
means, coordinates of the position of said cursor means on said
sheet means being the coordinates which are to be determined by
said apparatus;
a number of one-turn coils, arranged parallel to each other at an
equal interval on said sheet means, for detecting the magnetic flux
generated by said cursor means, the interval being set such that P
one-turn coils of said plurality of one-turn coils are covered by
said cursor means;
a number of signal lines which are fewer than the number of said
plurality of one-turn coils and which are connected to said
plurality of one-turn coils in a predetermined correspondence set
such that a combination of said signal lines to which given
adjacent P one-turn coils are connected differs from a combination
of said signal lines to which other given adjacent P one-turn coils
are connected;
detecting means for detecting a current flowing through said
respective signal lines;
calculating means for calculating the position coordinates of said
cursor means on said sheet means, said calculating means including
means for determining a course of position coordinates of said
cursor means on said sheet means by comparing amplitudes of
currents flowing through the respective given adjacent P one-turn
coils of said plurality of one-turn coils.
3. A frequency coupling position coordinates determination
apparatus comprising:
cursor means for generating a magnetic flux of a predetermined
frequency with respect to a position of said cursor on a sheet
means, coordinates of said position of the cursor means on said
sheet means being the coordinates which are to be determined by
said apparatus;
a number of one-turn coils, arranged parallel to each other at an
equal interval on said sheet means, for detecting the magnetic flux
generated by said cursor means, the interval being set such that P
one-turn coils of said plurality of one-turn coils are covered by
said cursor means;
a number of signal lines which are fewer than the number of said
plurality of one-turn coils and which are connected to said
plurality of one-turn coils in a predetermined correspondence set
such that a combination of said signal lines to which given
adjacent P one-turn coils are connected differs from a combination
of said signal lines to which other given adjacent P one-turn coils
are connected;
detecting means for detecting a current flowing through said
respective signal lines;
calculating means for calculating position coordinates of said
cursor means on said sheet means, said calculating means including
means for obtaining an area ratio of the one-turn coils located
below said cursor means on a basis of the currents flowing through
the respective one-turn coils, memory means for storing a
relationship between the area ratio and position coordinates, and
means for supplying an output from said area ratio obtaining means
to said memory means to obtain fine position coordinates of said
cursor means.
4. A frequency coupling, position coordinates determination
apparatus comprising:
cursor means for generating a magnetic flux of a predetermined
frequency with respect to a position of said cursor on sheet means,
coordinates of the position of said cursor means on said sheet
means being the coordinates to be determined by said apparatus;
a number of one-turn coils, arranged parallel to each other at an
equal interval on said sheet means, for detecting the magnetic flux
generated by said cursor means, the interval being set such that P
one-turn coils of said plurality of one-turn coils are covered by
said cursor means;
a number of signal lines which are fewer than the number of said
plurality of one-turn coils and which are connected to said
plurality of one-turn coils in a predetermined correspondence set
such that a combination of said signal lines to which given
adjacent P one-turn coils are connected differs from a combination
of said signal lines to which other given adjacent P one-turn coils
are connected;
detecting means for detecting a current flowing through said
respective signal lines;
first calculating means for calculating a course of the position
coordinates of said cursor means on said sheet means by comparing
amplitudes of currents flowing through the respective given
adjacent P one-turn coils of said plurality of one-turn coils;
and
second calculating means for calculating fine position coordinates
of said cursor means, said second calculating means including means
for obtaining an area ratio of the one-turn coils located below
said cursor means on the basis of the currents flowing through the
respective one-turn coils, memory means for storing a relationship
between the area ratio and position coordinates, and means for
supplying an output from said area ratio obtaining means to said
memory means to obtain the fine position coordinates of said cursor
means.
5. A frequency coupling position coordinates determination
apparatus comprising:
first and second sheets which are stacked;
a cursor for generating a magnetic flux of a predetermined
frequency with respect to said sheets;
a number of X coordinate one-turn coils, arranged parallel to each
other on said first sheet, for detecting the magnetic flux
generated by said cursor;
a number of Y coordinate one-turn coils, arranged parallel to each
other on said second sheet and perpendicular to said plurality of X
coordinate one-turn coils, for detecting the magnetic flux
generated by said cursor;
first and second signal lines which are fewer than the number of
said plurality of X coordinate and Y coordinate one-turn coils,
respectively, and which are connected to said plurality of X
coordinate and Y coordinate one-turn coils in a predetermined
correspondence, respectively, said predetermined correspondence
being set such that a combination of said first signal lines to
which a given adjacent P X coordinate one-turn coils are connected
differs from a combination of said first signal lines to which
another given adjacent P X coordinate one-turn coils are connected,
and a combination of said second signal lines to which a given
adjacent P Y coordinate one-turn coils are connected differs from a
combination of said second signal lines to which another given
adjacent P Y coordinate one-turn coils are connected;
detecting means for detecting a current flowing through said first
and second signal lines; and
calculating means for calculating X and Y position coordinates of
said cursor means on said first and second sheets on the basis of
an output of said detecting means.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a frequency coupling position
coordinates determination apparatus using an electromagnetic
induction system, or to a daisy type or a data tablet.
In a conventional position coordinates determination apparatus of
this type, a current flows through an electromagnetic coil provided
to a pen or cursor, and a magnetic flux generated from the
electromagnetic coil is detected by a plurality of one-turn coils
arranged on a flat plate, thereby determining a position of the pen
or cursor on the basis of a detection result.
FIG. 1 shows an example of such a conventional apparatus. A
position coordinates determination apparatus shown in FIG. 1 has a
circular coil 1 incorporated in a pen or cursor, and N (positive
integer) one-turn coils 2-1, 2-2, . . . , 2-k, 2-(k+1), . . . ,
2-(N-1) and 2-N arranged on a printed circuit board 3. The circular
coil 1 freely moves on an area 4 of the printed circuit board 3
where coordinate reading is performed. In the example shown in FIG.
1, the circular coil 1 is placed on the one-turn coils 2-k and
2-(k+1). In this case, when a current flows through the circular
coil 1, an induced current flows through the one-turn coils 2-k and
2-(k+1) and does not flow through the other one-turn coils. If it
is determined whether the induced current flows through the
respective one-turn coils or an amplitude of the flowed induced
current is determined, a current X position coordinate of the
circular coil 1 in the area 4 can be calculated. This conventional
apparatus also includes detectors 5-1, 5-2, . . . , 5-k, 5-(k-1), .
. . , 5-N for detecting the amplitude of the above induced current,
and a calculator 6 for calculating the current X position
coordinate of the circular coil 1 on the basis of the amplitude of
the N induced currents detected by the above detectors. The same
arrangement as described above is provided with respect to the Y
coordinate, so that X and Y position coordinates of the circular
coil 1 in the area 4 can be determined.
As described above, the conventional apparatus requires a large
number of detectors each constituted by integrated circuits,
resulting in a complex and large apparatus.
SUMMARY OF THE INVENTION
It is a principal object of the present invention to provide a
position coordinates determination apparatus which eliminates the
above conventional drawbacks and which is simple and small in
size.
A frequency coupling position coordinates determination apparatus
according to the present invention comprises cursor means for
generating a magnetic flux of a predetermined frequency with
respect to a position of said cursor on the sheet means the
coordinates of the position of the cursor means on the sheet means
being the coordinates which are to be determined by said apparatus,
a plurality of one-turn coils, arranged on the sheet means, for
detecting the magnetic flux generated by the cursor means, signal
lines connected to the plurality of one-turn coils in predetermined
correspondence, the signal lines being smaller in number than that
of the plurality of one-turn coils, detecting means for detecting a
current flowing through the respective signal lines, and
calculating means for calculating position coordinates of the
cursor means on the sheet means on the basis of an output from the
detecting means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a conventional apparatus;
FIG. 2 is a block diagram showing an arrangement of an embodiment
of the present invention;
FIG. 3 is a diagram showing an arrangement of a sheet 9 shown in
FIG. 2;
FIG. 4 is a flow chart for explaining an operation of the apparatus
shown in FIG. 2; and
FIG. 5 is a view for explaining a principle of coordinates
calculation of the apparatus shown in FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention will be described in detail with reference to
the accompanying drawings.
A position coordinates determination apparatus according to the
present invention shown in FIG. 2 is constituted by an X coordinate
reading sheet 9 having N X-axis one-turn coils and a bus 11
consisting of M signal lines connected to the X-axis one-turn coils
as described later, a Y coordinate reading sheet 10 having N Y-axis
one-turn coils and a bus 12 consisting of M signal lines connected
to the Y-axis one-turn coils, a selector 13, connected to the
signal lines of the bus 11, for selecting one of the signal lines,
an A/D converter 14 for converting a value of an output current or
voltage from the selector 13 into a digital value, a selector 15,
connected to the signal lines of the bus 12, for selecting one of
the signal lines, an A/D converter 16 for converting a value of an
output voltage from the selector 15 into a digital value,
processors 17 and 18, each incorporating a memory, for calculating
X and Y position coordinates on the basis of outputs from the A/D
converters 14 and 15, respectively, an interface circuit 20 for
supplying X and Y position coordinates obtained by the processors
17 and 18 to a calculator (not shown), a circular coil 19, an
oscillation amplifier 21 for flowing an AC current to the circular
coil 19, and a clock generator 22 for supplying clock signals to
the selectors 13 and 15, the A/D converters 14 and 16, and the
processors 17 and 18.
FIG. 3 shows an arrangement of the X coordinate reading sheet 9. In
FIG. 3, the number N of the one-turn coils is 10, and the number M
of the signal lines of the bus 11 is 5. Numbers M.sub.1 to M.sub.5
are assigned to the signal lines, respectively. Numbers N.sub.3,
N.sub.2, N.sub.1, N.sub.4, N.sub.5, N.sub.3, N.sub.4, N.sub.2,
N.sub.5, and N.sub.1 (to be referred to as a number row
hereinafter) are assigned to the 10 one-turn coils 9-1 to 9-10,
respectively, from the leftmost coil in FIG. 3. Each pair of
one-turn coils assigned with the same number is connected to a
corresponding one of the signal lines M.sub.1 to M.sub.5 assigned
with the same number. In addition, intervals between the one-turn
coils 9-1 to 9-10 are set such that two of the one-turn coils 9-1
to 9-10 are always located immediately below the circular coil 19.
The above-mentioned number row has the following characteristic.
That is, the same combination is not obtained by numbers of any
adjacent two one-turn coils 9-i and 9-(i+1). Therefore, if the
processor 17 determines two signal lines of the 5 signal lines
M.sub.1 to M.sub.5 which detect the induced current, two one-turn
coils of the one-turn coils 9-1 to 9-10 on which the circular coil
19 is located can be determined.
FIG. 4 is a flow chart for determining position coordinates of the
circular coil 19 executed in the processor 17. In steps S1 to S5 fo
FIG. 4, an amplitude of current of the signal line M.sub.i (i=1 to
5) in the bus 11 is A/D-converted by the A/D converter 14 and then
sequentially stored in an address (i: i=1 to 5) of a memory 17-1 in
the processor 17. In step S5, the memory 17-1 is searched to find
addresses m and n storing the maximum and second values. In step
S6, coarse position coordinates of the circular coil 19 are
calculated according to the addresses m and n. Therefore, a
position of the circular coil 19 can be first determined with an
accuracy of an interval between the one-turn coils.
Then, in step S7, a ratio of the induced currents detected by two
signal lines is obtained on the basis of the above maximum and
second values, thereby calculating a fine position of the circular
coil 19.
A method of accurately calculating central coordinates of each
one-turn coil in accordance with a ratio of induced currents
detected by the one-turn coils will be described below. FIG. 5
shows a state wherein the circular coil 19 is located across
one-turn coils 9-k and 9-(k+1). A hatched portion A is a portion of
the one-turn coil 9-k immediately below the circular coil 19, and a
hatched portion B is a portion of the one-turn coil 9-(k+1)
immediately below the circular coil 19. An area ratio of the
hatched portions A and B equals to a ratio of amplitudes of induced
currents respectively flowing through the one-turn coils 9-k and
9-(k+1). Therefore, assuming that an X coordinate of a center O of
the circular coil 19 is x, a radius thereof is r, an X coordinate
of the central line of the one-turn coil 9-k is l, an X coordinate
of a central line of the one-turn coil 9-(k+1) is (l+.DELTA.l), and
each width of the one-turn coils 9-k and 9-(k+1) is d, a
relationship between the ratio A/B of the areas A and B and (x-l)
is determined. Calculating means for converting the relationship
into numerals and stores it in, e.g., a ROM (Read Only Memory) in
the processor 17, and calculating (x-l) in accordance with the
ratio A/B can be easily arranged. This principle can be similarly
applied to the case wherein three or more one-turn coils are always
present immediately below the circular coil 19, and the coordinates
can be calculated in accordance with a formula as described above.
The X coordinate of the circular coil 19 obtained in this manner is
output as a position coordinate through the interface circuit
20.
The description has been made with reference to the X coordinate,
but the Y coordinate can be obtained in the processor 18 using the
same principle and the arrangement as those of the processor
17.
It is advantageous in designing the apparatus to increase the
number N of the one-turn coils and to decrease the number M of the
signal lines as much as possible. A problem of obtaining N and M is
to mathematically obtain a series of the maximum length (N) under
the condition that all of the R symbol partial rows have different
combinations in a series of a length N and consisting of M symbols.
This problem mathematically belongs to problems having no
systematic algorithm and hence can be obtained only by a one by one
calculation using a calculator. Note that R is the number of the
one-turn coils located immediately below the circular coil 19, and
R=2 in the above embodiment. Practically, N must be about 30, and
R=3. In this case, the following connection table can be
obtained.
As has been described above, according to the present invention,
the number of signal lines of a bus and that of A/D converters can
be decreased, so that the entire apparatus can be made smaller in
size.
______________________________________ Numbers of Numbers of
One-Turn Coils Signal Lines ______________________________________
(1) 4 (2) 3 (3) 2 (4) 6 (5) 7 (6) 4 (7) 5 (8) 6 (9) 7 (10) 1 (11) 2
(12) 5 (13) 3 (14) 4 (15) 6 (16) 1 (17) 2 (18) 3 (19) 7 (20) 4 (21)
1 (22) 3 (23) 5 (24) 6 (25) 1 (26) 3 (27) 7 (28) 5 (29) 1 (30) 4
(31) 2 ______________________________________
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